Gas treatment by catalytic ozone oxidation

ABSTRACT

In one embodiment, a catalyst for ozone oxidation of pollutant components dispersed in a gas is provided. The ozone oxidation catalyst has a porous body formed from a metal body, a ceramic, or polymeric fibers coated with metal. A catalytic noble metal composition is deposited on the surface of the porous body. The catalytic noble metal composition is formed from particles of a noble metal supported by a mesoporous molecular sieve.

RELATED APPLICATION

The subject application is a divisional of U.S. patent application. Ser.No. 12/900,768 (now U.S. Pat. No. 8,568,680), filed Oct. 8, 2010, andentitled “GAS TREATMENT BY CATALYTIC OZONE OXIDATION,” the entirety ofwhich is incorporated herein by reference.

FIELD

Embodiments described herein generally relate to catalysts and methodsfor ozone oxidation of pollutants dispersed in a gas.

BACKGROUND

Air purification devices are commonly employed in home, office andindustrial settings as a way to remove harmful components from theambient air and to improve air quality. Potentially harmful componentsthat can be found in the air include chemical pollutants, odors,airborne particles, bacteria and/or the like. Air purification devicescan be employed for many uses including treating the exhaust gases frommotor vehicles and other processes, for the generation of sterileenvironments and “clean” manufacturing facilities, and for removingpollutants that are commonly found in home, office and industrialenvironments.

Volatile organic compounds (VOCs) are gaseous phase organic compoundsthat are present in the environment from a variety of sources. VOCs arecan be outgassed by common manufactured items found in home and officesettings such as carpets, paint, cleaners, furniture, and plastics aswell as sources such as cigarette smoke or exhaust from passingautomobiles. VOCs are also produced across a range of industrialprocesses including refineries, semi-conductor manufacturing plants, andchemical manufacturing including paints, coatings, pharmaceuticals.

The levels of pollutants such as VOCs can be 2-5 times higher indoorscompared to outdoor levels. Mechanical ventilation systems can helpdecrease the levels of indoor pollutants depending upon the levels ofpollutants found in the outside environment. A mechanical ventilationsystem can turnover an indoor air volume as the rate of 1 to 3 hr⁻¹,while the turnover rate can be as low as 0.1 to 0.4 hr⁻¹ withoutmechanical ventilation. The largest reduction of airborne pollutantsincluding VOCs can be achieved by directly treating air to removepollutants or to convert pollutants to harmless byproducts.

SUMMARY

The following presents a simplified summary of one or more embodimentsin order to provide a basic understanding of some aspects of the subjectdisclosure. This summary is not an extensive overview. It is intended toneither identify key or critical elements of various embodiments nordelineate the scope of such embodiments. Its sole purpose is to presentsome concepts of the various embodiments in a simplified form as aprelude to the more detailed description that is presented later.

The ozone oxidation catalyst and methods for performing ozone oxidationdisclosed herein provide for the removal of gas-phase pollutants withincreased efficiency while exhibiting a low pressure drop across theozone oxidation catalyst. The ozone oxidation catalyst is formed bydepositing a catalytic noble metal composition on the surface of aporous body. The porous body is a solid body that is not a powder ornon-rigid material and maintains its shape under moderate pressure orthe influence of gravity.

A catalytic noble metal composition is applied to the surface of theporous body. The catalytic composition is formed from a noble metalsupported on a mesoporous molecular sieve. Efficiency of the ozoneoxidation catalyst is enhanced by high hydrophobicity and absorption ofpollutants by the molecular sieve material. Further, the porous bodyprovides for a high surface area for distribution of the catalytic noblemetal composition. High porosity decreases the pressure drop across theozone oxidation catalyst providing for a smaller resistance to diffusionof pollutants across the catalyst and higher space velocities of airflow through the ozone oxidation catalyst.

One aspect is directed toward an ozone oxidation catalyst formed bydepositing a catalytic noble metal composition having a noble metal anda mesoporous molecular sieve support on the surface of a porous body.

Another aspect is directed toward a method for removing pollutants froma gas. The gas is passed across an ozone oxidation catalyst formed bydepositing a catalytic noble metal composition having a noble metal anda mesoporous molecular sieve support on the surface of a porous body.

Yet another aspect is directed toward an apparatus for removingpollutants from the air by ozone oxidation. An ozone oxidation catalystis formed by depositing a catalytic noble metal composition having anoble metal and a mesoporous molecular sieve support on the surface of aporous body. The ozone oxidation catalyst is placed in a reactor inorder to facilitate contact between the ozone oxidation catalyst and agas. A fan or pump for moving air or another gas is provided to form agas flow moving into the reactor and over the ozone oxidation catalyst,where an ozone generator or ozone source is employed to add ozone to thegas flow.

BRIEF DESCRIPTION OF DRAWINGS

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the Office upon request and paymentof the necessary fee.

FIG. 1 shows an exemplary porous body in accordance with aspects of oneor more embodiments described herein.

FIGS. 2A and 2B show exemplary mesoporous molecular sieves in accordancewith aspects of one or more embodiments described herein.

FIG. 3 shows an exemplary noble metal catalytic composition inaccordance with aspects of one or more embodiments described herein.

FIGS. 4A and 4B show an exemplary ozone oxidation catalyst in accordancewith aspects of one or more embodiments described herein.

FIGS. 5A and 5B show schematics of an ozone oxidation catalyst employedas a filter inside of a reactor in accordance with aspects of one ormore embodiments described herein.

FIG. 6 shows an exemplary apparatus for monitoring the performance ofthe ozone oxidation catalyst.

FIG. 7 shows an exemplary apparatus for removing pollutants from the airor a gas using an ozone oxidation catalyst.

FIG. 8 shows a flow chart for removing pollutants from the air or a gasin accordance with aspects of one or move embodiments described herein.

DETAILED DESCRIPTION

Air can potentially contain many pollutants, organisms and substancesthat are potentially delirious to human health. For examples, the aircan contain suspended particles such as dust, pollen, viruses, bacteria,mold, spores, asbestos and particulate suspensions generated by tobaccosmoke and combustion engines. Further, the air can contain gas-phasepollutants such as carbon monoxide, formaldehyde, and volatile organiccompounds. Gas-phase pollutants can be created from combustion or fromliving organisms such as mold and can also be outgassed by many productsincluding building materials, carpets, furniture and cleaning productscommon in home and office environments. An additional source ofgas-phase pollutants includes radioactive gases such as radon that canenter buildings through rocks and from mineral building materials suchas granite.

Pollutants can bring about many undesirable health consequences.Particulate and gas-phase pollutants can directly affect eye and mucousmembrane irritation, allergies, the development of cancer, therespiratory system, the liver, the immune system, the reproductivesystem, and the nervous system. The level of pollutants found indoorscan be from about two to five times higher that the level of pollutantsfound outdoors. The U.S. Environmental Protection Agency recognizes“Sick-Building Syndrome” as a potential result of poor indoor airquality (IAQ). Sick-Building Syndrome can generate symptoms such asheadache, fatigue, skin and eye irritations, and respiratory illnesses.The EPA recognizes poor ventilation and chemical pollutants from bothindoor and outdoor sources as contributing factors to Sick-BuildingSyndrome.

Filters are often employed to remove particulate pollution. Particulatepollution becomes physically entrapped in a filter having a pore sizecomparable to the size of the particulate pollutants. However, gas-phasepollutants are individual molecules and cannot easily be filtered fromthe air based on physical size properties. A significant source ofgas-phase pollutants are volatile organic chemicals (VOCs), which isdefined as any organic compound having a high enough vapor pressuresunder normal conditions to significantly vaporize and enter thesurrounding atmosphere. VOCs are not limited to any particular chemicalidentity and can be hydrocarbons having alkane, alkene, alkyne,aldehyde, ketone, carbonyl, amine, alcohol, aromatic, and halofunctional groups. VOCs also include amines such as ammonia, urea andhaloamines although such compounds do not include carbon. Normalconditions are defined by an atmospheric pressure from about 95 to about105 kPa, where standard atmospheric pressure is 101.325 kPa andtemperature is from about −10° C. to about 50° C.

Examples of VOCS include benzene, toluene, ethylbenzene, xylenes,1,2,4-trimethylbenzene, acetone, ethyl alcohol, isopropyl alcohol,methacrylates (methyl or ethyl), ethyl acetate, tetrachloroethene,perchloroethene (PERC), trichloroethene (TCE), d-limonene (citrus odor),a-pinene (pine odor), isoprene, tetrahydrofuran, cyclohexane, hexane,butane, heptane, pentane, 1,1,1-trichloroethane, methyl-iso-butyl ketone(MIBK), methylene chloride, carbon tetrachloride, methyl ethyl ketone,1,4-dichlorobenzene, naphthalene, Freons (trichlorofluoromethane,dichlorodifluoromethane), and formaldehyde.

Organic molecules including VOCs can be degraded to carbon dioxide andwater by catalytic ozone oxidation. Ozone is capable of dissociatinginto an oxygen atom radical and molecular oxygen under properconditions. Oxygen radicals are highly reactive and are capable ofreacting with almost any organic molecule or material. Catalysis can beachieved by employing a surface capable of absorbing ozone and organicpollutants. A noble metal present on the surface of the ozone oxidationcatalyst provides a site for ozone decomposition into molecular oxygenand an oxygen radical. The formed oxygen radical can react withvirtually any organic compound to degrade the organic molecule to carbondioxide and water. Equations 1 through 7 show an exemplary process forthe degradation of methane to carbon dioxide and water.O₃+^(#)→O^(#)+O₂  (1)O₂+2*

2O*  (2)CH₄+O^(#→CH) ₄O^(#)  (3)CH₄+O*→CH₄O*  (4)CH₄O*+O^(#)→CH₂O*+H₂O+^(#)  (5)CH₂O*+O^(#)→CO*+H₂O+^(#)  (6)CO*+O^(#)→CO₂+*+#^(#)  (7)

In equations 1-7, the “*” symbol represents an absorption size foroxygen that can be a noble metal, a protonated (H) site or an alkali ionsite on the ozone oxidation catalyst. As shown in equation 2, the ozoneoxidation catalyst has the ability to breakdown molecular oxygen tooxygen radicals. In equations 1-7, the “#” symbol represents a site forthe absorption and decomposition of ozone that can be a noble metal orLewis acid site on the ozone oxidation catalyst. Equation 1 shows thebreakdown of ozone into an oxygen radical that remains adsorbed on theozone oxidation catalyst and molecular oxygen that can released as aproduct.

Equations 1-2 show the generation of oxygen radicals that can go on tooxidize a pollutant present in a gas flow passing over the ozoneoxidation catalyst. Equations 3-4 show the initial reaction of thegenerated oxygen radicals with a pollutant such as methane. Equations5-7 show the stoichiometry required to breakdown a hydrocarbon, such asmethane, to carbon dioxide and water.

An ozone oxidation catalyst having advantageous features for thecatalytic ozone oxidation of VOCs and other pollutants will be describedwith reference to the Figures. Methods and apparatuses for performingcatalytic ozone oxidation will also be described. The ozone oxidationcatalyst has several advantageous properties. The ozone oxidationcatalyst described herein is capable of effectively catalyzing ozoneoxidation at ambient temperatures. Further, the ozone oxidation catalystdescribed herein is capable of exhibiting a low pressure drop in a gasflow moving across the ozone oxidation catalyst. The ozone oxidationcatalyst also provides a large catalytic surface per unit volume overwhich a gas flow can pass allowing for more efficient mixing of oxygenradicals and pollutants. As such, an efficient catalyst for the removalof pollutants from gas can be made in a smaller packaging volume.

The ozone oxidation catalysts are formed from a porous body thatprovides the substrate for which to provide a catalytic surface. Theporous body can be a metal foam, meta-coated non-woven fiber or a porousceramic. The porous body is coated with a particulate material having 1)a particulate mesoporous molecular sieve material; and 2) particles of anoble metal that are supported by the particulate mesoporous molecularsieve material. The porous body can be made from a solid metallicmaterial or a polymer or fibrous material coated with metal to from ametallic surface. Further, a porous ceramic can be used as the porousbody. The porous body has a cellular structure having from about 40% toabout 90% of volume being void spaces. In another embodiment, the porousbody has from about 50% to about 90% of the volume being void spaces.The metal material making up the porous body and the void spaces arepresent and distributed in a three-dimensional space.

In one embodiment, the porous body is a nickel foam. In one embodiment,the porous body has from about 60 to about 200 pores per inch. Inanother embodiment, the porous body has from about 75 to about 150 poresper inch. In yet another embodiment, the porous body has from about 80to 120 pores per inch.

The porous body has a rigid or semi-rigid form. That is, the porous bodyhas a cellular shape that maintains a shape; the porous body does notflow under the influence of gravity nor does the porous body take theshape of a new container. In one embodiment, the thickness of the porousbody in the smallest dimension is from about 0.25 to about 5 cm. Inanother embodiment the thickness of the porous body in the smallestdimension is from about 0.5 to about 3 cm. In yet another embodiment,the thickness of the porous body in the smallest dimension is from about0.5 to about 2 cm.

FIG. 1 shows a micrograph of an exemplary nickel metal foam with scaleas shown. As can be seen in FIG. 1, the nickel foam forms athree-dimensional porous “web.” The nickel foam does not have a“honeycomb” structure. As defined herein, a “honeycomb” structure is asurface formed by plural two-dimensional planes formed substantiallyparallel to an axis, the plural two-dimensional planes forming a polygoncross-section in a plane substantially perpendicular to the axis.Examples of polygons include triangles, rectangles, pentagons andhexagons and include both equilateral and non-equilateral polygons.

A catalytic noble metal composition is applied to the surface of theporous body to form the ozone oxidation catalyst. The catalytic noblemetal composition is formed by combining a mesoporous molecular sievematerial and a noble metal. The mesoporous molecular sieve is used as asupport for the noble metal. The mesoporous molecular sieve can be amesoporous silicate molecular sieve, which is known and can be formed bycalcination of aluminosilicates in the presence of a surfactant.Suitable mesoporous silicon dioxide molecular sieves include MCM-41(Mobil Crystalline Material), which is composed of a silicate arrangedto form non-intersecting hexagonal channels.

FIG. 2 shows a transmission electron microscopy (TEM) micrograph ofMCM-41 provided as a particulate material. The particles shown in FIG.2B have a mean particle diameter of 110 angstroms and the pores have amean diameter of 31 angstroms. The MCM-41 particles shown in FIG. 2 aresuitable for forming the catalytic noble metal composition describedherein.

Those skilled in the art will recognize that other mesoporous molecularsieve materials, in addition to or in substitute for MCM-41, can be usedas a support. For example, SBA-15 can be successfully used as amesoporous molecular sieve material. Similar to MCM-41, SBA-15 is a typeof mesoporous zeolite formed from calcined silicates in the presence ofsurfactants. The mesoporous molecular sieve materials are not limited toa specific chemical identity provided that the molecular sieve used as asupport has a mesoporous pore structure.

In one embodiment, a mesoporous molecular sieve has pores with a meandiameter from about 5 to about 500 angstroms. In another embodiment, themesoporous molecular sieve has pores with a mean diameter from about 5to about 20 angstrom. In yet another embodiment, the mesoporousmolecular sieve has pores with a mean diameter from about 20 to about500 angstroms. In still yet another embodiment, the mesoporous molecularsieve has pores with a mean diameter from about 50 to about 500angstroms.

The mesoporous molecular sieve is provided as a particulate material.The mesoporous molecular sieve is mixed with at least one noble metalprovided in a particular form to form a catalytic composition. Thecatalytic composition having a mesoporous molecular sieve and a noblemetal is applied to the surface of the described porous body to form theozone oxidation catalyst.

The catalytic composition applied to the surface of the porous bodycontains at least one noble metal and a mesoporous molecular sieve asdescribed herein. Noble metals include ruthenium, rhodium, palladium,silver, osmium, iridium, platinum and gold. In one embodiment, themesoporous molecular sieve has a mean particle size from about 60 toabout 250 nm. In another embodiment, the mesoporous molecular sieve hasa mean particle size from about 75 to about 150 nm. In yet anotherembodiment, the mesoporous molecular sieve has a mean particle size fromabout 80 to about 125 nm. In one embodiment, the noble metal has a meanparticle size from about 5 to about 30 nm. In another embodiment, thenoble metal has a mean particle size from about 5 to about 25 nm. In yetanother embodiment, the noble metal has a mean particle size from about5 to about 15 nm.

The deposition of the catalytic composition onto the porous body canoptionally be assisted by combination with a binder material. Theidentity of the binder material is not limited to any specific material.However, the binder material can be a SiO₂ material having a meandiameter from about 10 to about 40 nm.

FIG. 3 shows a transmission electron microscopy (TEM) micrograph of anexemplary noble metal catalytic composition. Two different views of thecatalytic composition are shown. The exemplary catalytic composition isformed from Pd having a mean particle diameter of 10 nm supported on aMCM-41 molecular sieve having a mean particle diameter of 110 nm. Theloading of Pd is 4.1% by weight based on the weight of the porousmolecular sieve (MCM-41). Dark areas indicate the presence of Pd whilelight areas indicate the presence of MCM-41 without Pd.

FIGS. 4A and 4B show an exemplary oxidation catalyst formed by applyingthe noble metal catalytic composition to a Ni foam porous body. Thenoble metal catalytic composition shown in FIG. 3 is applied to the Nifoam porous body shown in FIG. 1 at a loading of 8.3 wt % of thecatalytic composition, where weight percent is based upon the weight ofthe Ni foam porous body. FIGS. 4A and 4B show micrographs of the sameexemplary ozone oxidation catalyst at different magnifications, asshown. In one embodiment, the weight of noble metal is less than about1% of the weight of the porous body. In another embodiment, the weightof the noble metal is less than about 0.5% of the weight of the porousbody. As can be seen with particularity in FIG. 4B, the catalyticcomposition of the noble metal supported on a mesoporous molecular sieveis disturbed on the surface of the porous body while maintaining theparticulate form of the catalytic composition. There is no requirementfor the catalytic composition to be evenly distributed on the surface ofthe porous body. Further, deposition of the catalytic composition on thesurface of the porous body does not modify the size or distribution ofthe pores and passageways formed through the porous body.

The ozone oxidation catalyst can be placed in a container or reactorchamber 501 to assist in the passage of a gas flow containing one ormore pollutants over the ozone oxidation catalyst 502, as shown in FIG.5A. The direction of the gas flow is along the longitudinal axis of thereactor chamber 501. The shape of the container is not limited to anyparticular shape or dimensions. However, the ozone oxidation catalyst502 can be placed in the reactor chamber 501 such that all air passingfrom an inlet 503 of the container to an outlet 504 of the containerpasses through the ozone oxidation catalyst 502. As such, the ozoneoxidation catalyst 502 acts as a filter and can be referred to as anozone oxidation filter. The ozone oxidation catalyst 502 can be providedin the container 501 with a planar or about planar face of the filter502 arranged to be perpendicular to the direction of flow of the gasflow 505. In one embodiment, the smallest dimension of the ozoneoxidation catalyst is arranged to be about parallel to the direction ofthe gas flow 505. In one embodiment, the thickness of the ozoneoxidation catalyst in the direction of gas flow is from about 0.25 toabout 5 cm. In another embodiment the thickness of the ozone oxidationcatalyst in the direction of gas flow is from about 0.5 to about 3 cm.In yet another embodiment, the thickness of the ozone oxidation catalystin the direction of gas flow is from about 0.5 to about 2 cm.

FIG. 5B shows a schematic representation of a cross-section of the ozoneoxidation catalyst 502. The volume of the ozone oxidation catalystfilter 502 includes the solid component of the Ni metal foam 510 and thevoid spaces 512 accounting for the porosity of the ozone oxidationcatalyst filter 502. The surface of the solid component of the Ni metalfoam 510, which is the solid component of the porous body, is studdedwith the catalytic composition 514 described above. The insert to FIG.5B shows that each particle of the catalytic composition 514 containsnoble metal particles 516 on mesoporous molecular sieve material 518.

A feature of the ozone oxidation catalysts taught herein is that thereis a small pressured drop experience by a gas flow passing over thecatalyst. The porous body through which the ozone oxidation catalyst isformed provides for a low impediment to gas flow compared to catalyststructures composed of a bed of backed particles. The ozone oxidationcatalyst can be provided in a reactor, as described above, such that theozone oxidation catalyst has a first side and a second side. In oneembodiment, the pressure on the second side of the ozone oxidationcatalyst is within about 30% of the pressure on the first side of theozone oxidation catalyst when a gas flow is passing through the ozoneoxidation catalyst at a space velocity from about 10000 to about 75000hr⁻¹. In another embodiment, the pressure on the second side of theozone oxidation catalyst is within about 20% of the pressure on thefirst side of the ozone oxidation catalyst when a gas flow is passingthrough the ozone oxidation catalyst at a space velocity from about10000 to about 75000 hr⁻¹. In yet another embodiment, the pressure onthe second side of the ozone oxidation catalyst is within about 20% ofthe pressure on the first side of the ozone oxidation catalyst when agas flow is passing through the ozone oxidation catalyst at a spacevelocity from about 10000 to about 75000 hr⁻¹. The first side of theozone oxidation catalyst is closer to the inlet of the reactor;therefore, the pressure on the first side of the ozone oxidationcatalyst is greater than on the second side.

Ozone oxidation is particularly advantageous over alternative methodsfor removing gas-phase pollutants from gases, such as air ionization, byallowing for operation at ambient temperature. In one embodiment, ozoneoxidation with the ozone oxidation catalyst is done at a temperaturefrom about −10° C. to about 50° C. In another embodiment, ozoneoxidation with the ozone oxidation catalyst is done at a temperaturefrom about 0° C. to about 40° C. In yet another embodiment, ozoneoxidation with the ozone oxidation catalyst is done at a temperaturefrom about 0° C. to about 30° C. In an additional embodiment, ozoneoxidation with the ozone oxidation catalyst is performed on ambient airwithout actively changing the temperature of the ambient air.

FIG. 6 shows a schematic apparatus for measuring the effectiveness of anexemplary ozone oxidation catalyst. All of the components of theapparatus shown in FIG. 6 are not required in order for an ozoneoxidation catalyst to be employed to reduce pollutants in the air orother gas. Rather, the setup shown in FIG. 6 is an example apparatusused to measure the effectiveness and efficiency of an ozone oxidationcatalyst as described herein.

In FIG. 6, a source of air 602 and source of pollutant 604 are providedsuch that the rate of flow of air 602 and pollutant 604 can be adjustedby mass flow controllers 606 and 608, respectively. A bubbler 610 isattached in-line with the pollutant source 604 to generate small flowsof pollutants. The flows originating from the air source 602 andpollutant source 604 are combined prior to introduction to reactor 612.An ozone generator 614 or another source of ozone is attached forintroducing ozone into the reactor 612. As such, the gas flow 616introduced into the reactor 612 contains air containing nitrogen andoxygen form the air source 602, pollutant from the pollutant source 604and ozone from the ozone generator 614.

The reactor 612 contains an ozone oxidation filter 618 that contains theozone oxidation catalyst. The gas flow 616 can be passed through thereactor 612 or diverted through a bypass 620 such that the compositionof the gas flow 616 can be measured without treatment by the filter 618.The gas flow 616 or the effluent from the reactor 612 is passed to ananalytical device 622. The analytical device 622 can be a FTIRspectrometer that is suitable for measuring the presence of manydifferent kinds of VOCs, where data collected by a computer 624. Gasflow is passed to exhaust 626 after analysis. Also shown in FIG. 6,several valves 630 are used to control the movement of gasses throughthe apparatus.

The effectiveness of the ozone oxidation catalyst was measured using acatalyst filter prepared from a nickel foam porous body having 110 poresper inch. A catalytic composition having 4.1 weight % Pd loaded on aMCM-41 mesoporous support was applied to the surface of the nickel foamporous body; the mean particle diameter of the Pd and MCM-41 was 10 and110 nm, respectively. Loading of the catalytic composition onto thenickel foam porous body was 8.3 weight %. The ozone oxidation catalystwas formed into a shape to fit a reactor fashioned from a stainlesssteel cylinder with a diameter of 5.3 cm and a length 10 cm. Thethickness of the ozone oxidation catalyst filter in the direction of airflow was 1.5 cm. That is, the ozone oxidation catalyst filter occupied15% of the length of the stainless steel cylinder used as the reactor.

Table 1 shows the dependency of the ozone oxidation filter and ozone forthe removal of pollutants. A gas flow of a 4:1 mixture of nitrogen andoxygen having an ozone concentration of 510 ppm (parts per million) atthe inlet of the reactor 612 was passed through the reactor 612. Thespace velocity of the gas flow through the reactor 612 was maintained at33481 hr⁻¹. Toluene was used as an exemplary VOC (pollutant) andprovided at a concentration of 21.3 ppm at the inlet of the reactor 612except in run number 2 where toluene was omitted. Each run was performedfor two hours at a temperature of 25° C.

TABLE 1 Comparative toluene removal efficiency under differentarrangements of the ozone oxidation catalytic filter and inlet gas flowcomponents Toluene Inlet toluene Outlet toluene Outlet ozone removalconcentration concentration concentration efficiency Run Arrangement(ppm) (ppm) (ppm) (%) 1 Air + filter 21.3 21.3 —  0.0 2 Ozone + filter —— 413 — 3 Air + ozone 21.3 18.7 491 12.2 4 Air + ozone + 21.3  8.1  6762.0 filter

As shown in Table 1, the ozone oxidation filter and ozone is requiredfor significant removal of toluene. Run 2 indicates that ozone breakdownby the ozone oxidation filter is partial and not done with completeefficiency. Run 3 indicates that ozone has some ability to react withVOCs such as toluene without the presence of the filter. Run 4 shows asignificant reduction in the amount of toluene at 62%.

The concentration of ozone detected at the outlet of ozone oxidationfilter for Run 4 is significantly less than for Run 2. The ozoneoxidation filter catalyzes two separate chemical processes: 1) breakdownof ozone to molecular oxygen and oxygen radicals; and 2) reaction ofradical oxygen with a VOC. Without wishing to be bound by any oneparticular theory, it is possible that the high level of ozone observedat the outlet in Run 2 is the result of some of the radical oxygengenerated reacting with molecular oxygen to reform ozone. In Run 4, thereaction of oxygen radicals with toluene allows for the removal of theoxygen radicals to drive the equilibrium toward breaking down a higherpercentage of the ozone present at the inlet of the gas flow.

In Table 2, the amount of toluene in the gas flow is varied to observethe affect on toluene removal efficiency. An ozone catalytic filterhaving the same composition as Table 1 was used for the runs shown onTable 2.

Conditions were a carrier gas of 4:1 mixture of nitrogen and oxygen anda space velocity of 33481 hr⁻¹. Inlet ozone concentration was 510 ppmand each run was performed at 25° C. for two hours.

TABLE 2 Comparative toluene removal efficiency under varying inletconcentrations of toluene Toluene Inlet toluene Outlet toluene Outletozone removal concentration concentration concentration efficiency Run(ppm) (ppm) (ppm) (%) 1 11.6 3.8 114 67.2 2 21.3 8.1 67 62.0 3 42.4 19.649 53.8

As shown in Table 2, toluene removal efficiency is decreased as tolueneconcentration at the inlet is increased from 11.6 to 42.4 ppm. Whileefficiency of toluene removal decreases as toluene levels increase, thetotal amount of toluene removed and the utilization rate of ozone bothincrease.

In one embodiment, the ozone oxidation catalyst removes from about 40 toabout 75% of the VOCs in a gas flow where the gas flow contains fromabout 5 to about 75 ppm of VOCs. In another embodiment, the ozoneoxidation catalyst removes from about 40 to about 65% of the VOCs in agas flow where the gas flow contains from about 5 to about 75 ppm ofVOCs. In yet another embodiment, the ozone oxidation catalyst removesabout 40% or more of the VOCs in a gas flow where the gas flow containsfrom about 5 to about 75 ppm of VOCs.

In Table 3, the amount of ozone present in the gas flow passed over theozone oxidation catalyst is varied. An ozone catalytic filter having thesame composition as Table 1 was used for the runs shown on Table 3.Conditions were a carrier gas of 4:1 mixture of nitrogen and oxygen anda space velocity of 33481 hr⁻¹. Inlet toluene concentration was 21.3 ppmand each run was performed at 25° C. for two hours.

TABLE 3 Comparative toluene removal efficiency under varying inletconcentrations of ozone Toluene Inlet ozone Inlet toluene Outlet tolueneOutlet ozone removal concentration concentration concentrationconcentration efficiency Run (ppm) (ppm) (ppm) (ppm) (%) 1 510 21.3 8.167 62.0 2 1019 21.3 5.7 626 73.2 3 1631 21.3 4.0 1048 81.2

As shown in Table 3, an increase in the inlet concentration of ozoneincreases toluene removal efficiency. However, the outlet ozoneconcentration rises significantly and the overall efficiency of ozoneutilization is increased. Optionally, the gas flow emitted from ozoneoxidation catalyst can be passed through an additional filter, such asan activated carbon filter, to remove ozone from the gas flow prior todischarge to the ambient air.

In one embodiment, the ozone oxidation catalyst removes from about 35 toabout 90% of the VOCs in a gas flow where the gas flow contains fromabout 250 to about 2000 ppm of ozone. In another embodiment, the ozoneoxidation catalyst removes from about 30 to about 85% of the VOCs in agas flow where the gas flow contains from about 250 to about 2000 ppm ofozone. In another embodiment, the ozone oxidation catalyst removes atleast about 50% of the VOCs in a gas flow where the gas flow containsfrom about 250 to about 2000 ppm of ozone.

In Table 4, the space velocity of the gas flow passed over the ozoneoxidation catalyst is varied. An ozone catalytic filter having the samecomposition as Table 1 was used for the runs shown on Table 4.Conditions were a carrier gas of 4:1 mixture of nitrogen and oxygen, aninlet toluene concentration was 21.3 ppm, an inlet ozone concentrationof 510 ppm and each run was performed at 25° C. for two hours.

TABLE 4 Comparative toluene removal efficiency under varying carrier gasspace velocity Toluene Inlet toluene Outlet toluene Outlet ozone removalSpace velocity concentration concentration concentration efficiency Run(hr⁻¹) (ppm) (ppm) (ppm) (%) 1 15487 21.3 6.1 44 71.4 2 33481 21.3 8.167 62.0 3 52924 21.3 13.4 241 37.1

As shown in Table 4, an increase in the space velocity of the gas flowover the ozone oxidation catalyst filter results in a decrease intoluene removal efficiency. The decrease in toluene removal efficiencyis likely the result of a decreased resident time of the reactants onthe ozone oxidation catalyst.

In one embodiment, the ozone oxidation catalyst removes from about 35 toabout 90% of the VOCs in a gas flow where the gas flow is passed overthe ozone oxidation catalyst at a space velocity from about 10000 toabout 75000 hr⁻¹. In another embodiment, the ozone oxidation catalystremoves from about 35 to about 85% of the VOCs in a gas flow where thegas flow is passed over the ozone oxidation catalyst at a space velocityfrom about 10000 to about 75000 hr⁻¹. In yet another embodiment, theozone oxidation catalyst removes at least about 50% of the VOCs in a gasflow where the gas flow is passed over the ozone oxidation catalyst at aspace velocity from about 10000 to about 75000 hr⁻¹.

One skilled in the art will readily understand that the concentration ofozone employed and the space velocity of the gas flow over the ozoneoxidation catalyst can be adjusted for different applications. Forexample, the amount of ozone can be increased and the space velocitydecreased for applications having a high level of pollutants. Inaddition to adjusting the velocity of the gas flow over the ozoneoxidation catalyst, the space velocity can be decreased by increasingthe volume of the ozone oxidation catalyst.

A device for removing pollutants from the air or other gas employing theozone oxidation catalyst does not require all of the components shown inFIG. 6. In reference to FIG. 7, a fan or pump 702 is used to drawambient air or another gas into a reactor 712 having a filter 718 formedfrom the ozone oxidation catalyst. An ozone generator or ozone source704 is provided to add a desirable amount of ozone to the gas enteringthe reactor 712. Alternatively, the ambient air or other gas enters thereactor 712 through a first inlet and the ozone from the ozone generatoror ozone source enters the reactor 712 through a second inlet. That is,there is no requirement for the gas containing the pollutants for ozoneoxidation and ozone to be mixed prior to entering the reactor 712. Thegas exiting the reactor 712 is passed on as exhaust 730. Optionallyadditional filters can be included in addition to the filter formed fromthe ozone oxidation catalyst. For example, a pre-filter for physicallyfiltering particulate matter, a plasma generator filter or a HEPA filtercan be used in conjunction with the ozone oxidation catalyst. Additionalfilters can be included in the reactor 712 along with the ozoneoxidation catalyst. Alternatively, additional filters can be providedfor separately for filtering the air flow entering the reactor or forfiltering the exhaust 730 from the reactor 712 prior to return to theenvironment.

In order to fully describe the innovations disclosed herein, acts forreducing or removing volatile organic compound from a gas will bedescribed with reference to FIG. 8. In act 802, ozone is added to a gashaving one or more volatile organic compounds dispersed therein. In act804, a gas flow having ozone and the one or more volatile organiccompounds is formed. In act 806, the gas flow having ozone and one ormore volatile organic compounds is passed over an ozone oxidationcatalyst. The ozone oxidation catalyst is formed from a porous body witha catalytic noble metal composition applied to a surface of the ozoneoxidation catalyst. The catalytic noble metal composition has a noblemetal supported on a mesoporous molecular sieve.

Other than in the operating examples, or where otherwise indicated, allnumbers, values and/or expressions referring to quantities ofingredients, reaction conditions, etc., used in the specification andclaims are to be understood as modified in all instances by the term“about.”

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the various embodiments described herein. Indeed, the novelmethods and structures described herein may be embodied in a variety ofother forms; furthermore, various omissions, substitutions and changesin the form of the methods and structures described herein may be madewithout departing from the spirit of the various embodiments. Theaccompanying claims and their equivalents are intended to cover suchforms or modifications as would fall within the scope and spirit of thevarious embodiments.

What is claimed is:
 1. A method for removing volatile organic compoundfrom a gas, comprising: adding ozone to a gas comprising one or morevolatile organic compounds forming a gas flow containing the one or morevolatile organic compounds and ozone; and passing the gas flow over afilter comprising an ozone oxidation catalyst including a porous bodyhaving a surface and a catalytic noble metal composition deposited onthe surface of the porous body, the catalytic noble metal compositioncomprising a mesoporous molecular sieve support and a noble metal. 2.The method of claim 1, further comprising: removing from about 35% toabout 90% of the volatile organic compounds in the gas flow and whereinthe passing includes passing the gas flow over the ozone oxidationcatalyst at a space velocity from about 10000 to about 75000 hr⁻¹. 3.The method of claim 1, wherein the noble metal of the ozone oxidationcatalyst is one or more selected from the group consisting of palladiumand platinum.
 4. The method of claim 1, wherein the one or more volatileorganic compounds are one or more selected from the group consisting ofbenzene, toluene, ethylbenzene, xylenes,1,2,4-trimethylbenzene, acetone,ethyl alcohol, isopropyl alcohol, methacrylates ethyl acetate,tetrachloroethene, perchloroethene, trichloroethene, d-limonene,a-pinene, isoprene, tetrahydrofuran, cyclohexane, hexane, butane,heptane, pentane, 1,1,1-trichloroethane, methyl-iso-butyl ketone,methylene chloride, carbon tetrachloride, methyl ethyl ketone,1,4-dichlorobenzene, naphthalene, trichlorofluoromethane,dichlorodifluoromethane, and formaldehyde.
 5. The method of claim 1,wherein the ozone oxidation catalyst has a first side and a second sidewhen present in a reactor, and the pressure of the gas flow on thesecond side of the ozone oxidation catalyst is within about 30% of thepressure of the gas flow on the first side of the ozone oxidationcatalyst, the pressure on the first side greater than on the secondside.
 6. The method of claim 1, wherein the mesoporous molecular sievesupport of the ozone oxidation catalyst is Mobil Crystalline Material 41and the noble metal is one or more selected from the group consisting ofpalladium and platinum.
 7. An apparatus, comprising: a mixing componentconfigured to add ozone to a gas comprising one or more volatile organiccompounds forming a gas flow comprising the one or more volatile organiccompounds and the ozone; and a filtration component configured to directthe gas flow in a direction of a filter comprising an ozone oxidationcatalyst comprising a porous body having a surface and a catalytic noblemetal composition deposited on the surface of the porous body, whereinthe catalytic noble metal composition comprises a mesoporous molecularsieve support and a noble metal.
 8. The apparatus of claim 7, furthercomprising a removal component configured to remove about 35% to about90% of the volatile organic compounds in the gas flow, wherein thedirecting comprises directing the gas flow in the direction of thefilter comprising the ozone oxidation catalyst at a space velocity fromabout 10000 to about 75000 hr⁻¹.
 9. The apparatus of claim 7, whereinthe noble metal of the ozone oxidation catalyst is at least one ofpalladium or platinum.
 10. The apparatus of claim 7, wherein the one ormore volatile organic compounds comprise at least one of benzene,toluene, ethylbenzene, xylenes,1,2,4-trimethylbenzene, acetone, ethylalcohol, isopropyl alcohol, methacrylates ethyl acetate,tetrachloroethene, perchloroethene, trichloroethene, d-limonene,a-pinene, isoprene, tetrahydrofuran, cyclohexane, hexane, butane,heptane, pentane, 1,1,1-trichloroethane, methyl-iso-butyl ketone,methylene chloride, carbon tetrachloride, methyl ethyl ketone,1,4-dichlorobenzene, naphthalene, trichlorofluoromethane,dichlorodifluoromethane, or formaldehyde.
 11. The apparatus of claim 7,wherein the ozone oxidation catalyst comprises a first side and a secondside, a second pressure of the gas flow on the second side of the ozoneoxidation catalyst is within about 30% of a first pressure of the gasflow on the first side of the ozone oxidation catalyst, and the firstpressure on the first side is greater than the second pressure on thesecond side.
 12. The apparatus of claim 7, wherein the mesoporousmolecular sieve support of the ozone oxidation catalyst is MobilCrystalline Material 41 and the noble metal comprises at least one ofpalladium or platinum.
 13. A system, comprising: means for adding ozoneto a gas comprising one or more volatile organic compounds forming a gasflow comprising the one or more volatile organic compounds and theozone; and means for passing the gas flow toward a filter comprising anozone oxidation catalyst including a porous body having a surface and acatalytic noble metal composition deposited on the surface of the porousbody, the catalytic noble metal composition comprising a mesoporousmolecular sieve support and a noble metal.
 14. The system of claim 13,further comprising means for removing about 35% to about 90% of the oneor more volatile organic compounds in the gas flow and wherein means forpassing comprises means for passing the gas flow toward the ozoneoxidation catalyst at a space velocity from about 10000 to about 75000hr⁻.
 15. The system of claim 13, wherein the noble metal of the ozoneoxidation catalyst comprises at least one of palladium or platinum. 16.The system of claim 13, wherein the one or more volatile organiccompounds comprises at least one of benzene, toluene, ethylbenzene,xylenes,1,2,4-trimethylbenzene, acetone, ethyl alcohol, isopropylalcohol, methacrylates ethyl acetate, tetrachloroethene,perchloroethene, trichloroethene, d-limonene, a-pinene, isoprene,tetrahydrofuran, cyclohexane, hexane, butane, heptane, pentane,1,1,1-trichloroethane, methyl-iso-butyl ketone, methylene chloride,carbon tetrachloride, methyl ethyl ketone, 1,4-dichlorobenzene,naphthalene, trichlorofluoromethane, dichlorodifluoromethane, orformaldehyde.
 17. The system of claim 13, wherein, in a reactor, theozone oxidation catalyst comprises a first side and a second side, and asecond pressure of the gas flow on the second side of the ozoneoxidation catalyst is within about 30% of a first pressure of the gasflow on the first side of the ozone oxidation catalyst, the firstpressure on the first side being greater than the second pressure on thesecond side.
 18. The system of claim 13, wherein the mesoporousmolecular sieve support of the ozone oxidation catalyst is MobilCrystalline Material 41 and the noble metal is at least one of palladiumor platinum.
 19. The system of claim 13, further comprising means forgenerating the ozone.
 20. The system of claim 13, wherein the porousbody is at least one of a metal foam, meta-coated non-woven fiber, or aporous ceramic material.